In recent years, cellular mobile radio communication systems have been widely available. Therefore, communications are often performed between a mobile station such as a mobile terminal and a base transceiver station when a user boards a moving object such as a train. Further, the speed of moving objects has been increased with advances in transportation. Here, when a mobile station included in the mobile radio communication system moves with a high speed, the reception frequency of a radio signal transmitted from the mobile station to a base transceiver station is changed due to the Doppler effect. For example, in the case where the mobile station approaches the base transceiver station with a high speed, the frequency of a radio signal transmitted from the mobile station to the base transceiver station becomes higher than what is usually obtained. On the other hand, when the mobile station moves away from the base transceiver station with a high speed, the frequency of a radio signal transmitted from the mobile station to the base transceiver station becomes lower than what is usually obtained. Therefore, the base transceiver station compensates for a variance of the reception frequency through an automatic frequency control (AFC) circuit.
For example, Japanese national Publication of International patent Application No. 2001-504670 discloses a method of estimating the speed of a mobile station with precision. The above-described speed estimation method allows for calculating a frequency offset value for each reception burst in consideration of the Doppler shift of information, which occurs in the reception burst. The above-described speed estimation method allows for calculating the signal quality value for each burst and estimating the speed of a mobile station based on the average of frequency offset values, that is, signal quality values achieving at least a specified signal quality level of the calculated signal quality values.
A base transceiver station may measure a frequency deviation with high precision, where the frequency deviation is the difference between the frequency of a radio signal transmitted from a mobile station and a communication frequency that had already been set. Therefore, the base transceiver station determines a compensation value by averaging the frequency deviations of radio signals transmitted from a single mobile station within a specified measurement period. The time period during which the frequency deviations of the radio signals are measured may be long so as to measure the frequency deviations with high precision. On the other hand, when the mobile station is passing by the base transceiver station, the value of the frequency of a radio signal transmitted from the mobile station to the base transceiver station is steeply changed from a high value to a low value. If the frequency deviation of a radio signal is steeply changed as described above when the frequency deviation measurement period is long, it may be difficult for the AFC circuit of the base transceiver station to respond to the variance of the frequency deviation. In that case, it becomes difficult for the base transceiver station to decode a radio signal transmitted from the mobile station with precision so that the radio communication quality is deteriorated.